1. Field of the Invention
The invention pertains to the field of chain tensioners. More particularly, the invention pertains to a dual arm tensioner for tensioning strands flanking an auxiliary drive sprocket.
2. Description of Related Art
As a chain wears, the distance between the links increases, leading to an overall increase in the length of the chain over time. In many situations it is desirable to tension more than one strand of a multi-strand chain simultaneously. In an engine timing system having overhead cams, an auxiliary drive on the slack strand is often positioned such that one tensioning arm is incapable of absorbing the chain length increase due to wear, both above and below the auxiliary drive.
Using two separate tensioning systems is an obvious first consideration, but it is often desirable to tension two strands either proportionally or equally, and the probability of separate systems tensioning equally is unreliable, leaving the preferred approach to simultaneous reaction being connecting the two arms with pins and links.
Dual arm tensioners are known in the art.
In U.S. Pat. No. 6,322,469, “DUAL ARM CHAIN TENSIONER FOR CONTACTING MULTIPLE CHAIN STRANDS”, issued Nov. 27, 2001, the dual arms act on a tight and a slack strand and are moved laterally in the same direction by a common force.
In U.S. Pat. No. 6,322,470, “PIVOTING DUAL ARM CHAIN TENSIONER SYSTEM FOR CONTACTING MULTIPLE CHAIN STRANDS”, issued Nov. 27, 2001, the dual arms act on a tight and a slack strand and are moved toward each other during tensioning by a common pivoting lever.
In U.S. Pat. No. 6,358,169, “CHAIN TENSIONING SYSTEM HAVING A PIVOTING TENSIONER ARM”, issued Mar. 19, 2002, the dual arms act on a tight and a slack strand by rotation simultaneously about a common pivot point.
In Japanese Publication No. 62-024062, “CHAIN TENSIONER OF A V-ENGINE”, published Feb. 2, 1987, a push rod pushes a protrusion to rotate an arm body. Rotating the arm body pushes two arms attached to the arm body against the distal ends of two separate tensioner bands, thereby biasing the two tensioner bands against two chains of a v-type engine.
There is a need in the art for a dual arm chain tensioner for tensioning two slack strands simultaneously using a proportional tensioning force on the two strands.